One of the oldest methods known to mankind for preserving foodstuffs, namely, fruits, vegetables, and meats is to dehydrate them to the point where micro-organisms such as molds, bacterias and yeasts will not be able to reproduce in sufficient quantities to spoil the food for human consumption. Originally this was accomplished by means of placing a drying rack or table in the open air and sunshine. Indeed many such drying racks still exist along the beaches of Cape Cod which were used during colonial times for the dehydration of meats prior to their shipment to Europe.
The use of the sun for dehydration was at best a most unsatisfactory procedure since proper and optimum dehydration requires control of air flow, temperature and humidity. Additionally it is well known in the art that proper control of air flow, temperature and humidity will optimize retention of food coloring, flavoring, consistency and nutrient value.
In the past numerous food dehydrating apparatus have been developed. As a general rule all of these dehydrators have attempted to control humidity, which must be substantially below saturation, by means of a variable speed fan motor or a recirculation device of some sort. Additionally each of these devices has attempted to control dehydration temperature by preheating the air entering the dehydrator prior to its entry.
Additionally prior dehydrators have attempted to achieve uniform air flow past the numerous dehydration trays by means of either blowing the warm dry air vertically through the trays from bottom to top or horizontally between the trays by the use of numerous complicated air ducts, louvers and passageways such as those disclosed in Bills et al., U.S. Pat. No. 3,943,842.
If air ducts and/or adjustable louvers are used the result in an increase in costs of manufacture and usually a decrease in the drying capacity in relation to size and weight of the appliance.
In order to produce an economical, lighter and smaller dehydrator which would be better suited for household use, dehydrators were developed that did not utilize complicated ducts and baffling systems, but rather attempted to achieve uniform air flow by ducting the influent air into the dehydration chamber at the bottom and allowing it to blow or rise, through the various dehydration trays, normally constructed of screens or wire meshes, to the top where the effluent was either released to the atmosphere or recirculated to the influent chamber. While such dehydrators were more economical and lighter in weight, they cannot be used to dehydrate more than one type of food at the same time since cross flavoring will result. This results when air passing through one tray containing a particular food being dehydrated picks up certain flavoring elements which are then deposited upon food being dehydrated on a higher tray. Additionally vertical air flows often result in non-uniform dehydration rates with the resulting variations of consistency from one side of the dehydrated food to the other.
Bread and bakery product dough raising, when done commercially, often is accomplished through the use of a specially designed dough raising cabinet or other similar apparatus. These commercial devices are usually large and custom designed. Because of space requirements, costs, and the limited use to which a dough raising cabinet can be put, the household use of special dough raising cabinets has been limited.
Because of this, most household bakers rely upon the open air environment of the home and increased amounts of time to raise the bread dough. Usually the home baker will select the room with the most favorable conditions for dough raising and allow the bread to raise in a cloth covered pan for a number of hours prior to baking. The net result is that the home baker expends considerably more time, care and effort to produce bakery products than the commercial baker does.
In practice it has been found that the optimum environment for dough raising is an unventilated atmosphere with a temperature of 80.degree. F. to 90.degree. F. with a relative humidity in excess of 90%. While these conditions can be created during the summer months in most areas of the country, they cannot be achieved during the winter months or when home air conditioning is in use.
In effect, the environments for dehydrating foodstuffs and raising bakery product dough are mutually exclusive. When dehydrating foods, you are inhibiting the growth of yeasts, molds and bacteria, and when raising bakery product dough you are attempting to promote the growth of yeasts.